The background description includes information that may be useful in understanding the present invention. It is not an admission that any of the information provided herein is prior art or relevant to the presently claimed invention, or that any publication specifically or implicitly referenced is prior art.
Alternating current generators in which the stators utilize permanent magnets to provide the magnetic flux to armature coils suffer numerous disadvantages. Maintaining terminal voltage when an external load is connected to the generator, or when the external load varies, can be technologically challenging. Additionally, much of the magnetic flux from the permanent magnets is unused during operation of traditional generators that utilize magnets.
To address these problems, U.S. Pat. No. 2,816,240 to Zimmerman discloses a generator that includes field coils to maintain terminal voltage. Zimmerman's stator comprises two sets of circular laminations, one of which has two permanent magnets inserted into two angular segments removed from each lamination and oriented such that the like poles face each other. A flux-reversing multi-pole rotor acts as a flux reversing switch for the flux passing though the armature windings when successive teeth of the rotor are in alignment with the successive poles of the stator. When an external load is connected to the generator, excitation of the field coils maintains terminal voltage. However, Zimmerman fails to efficiently use magnetic flux from the stator permanent magnets, because Zimmerman's flux paths travel both through the rotor and around the stator circumference.
In U. S. Patent Application No. 2008/0272664, Flynn discloses electromechanical devices that have increased power density and efficiency. Flynn's electromechanical devices have stators comprised of alternating stator segments and permanent magnets. When Flynn's rotor shaft is rotated by external prime mover, Flynn's bridge and pole wound electro-mechanical device functions as a generator with stator segments having reluctance bridges with an air gap and a reluctance gap control coil. However, Flynn's electromechanical devices only decrease cogging torque without providing any motive force.
Thus, there is still a need for generators that utilize alternate magnetic paths to produce torque through the rotor and produce electricity through the stator in an energy-efficient manner.
All publications identified herein are incorporated by reference to the same extent as if each individual publication or patent application were specifically and individually indicated to be incorporated by reference. Where a definition or use of a term in an incorporated reference is inconsistent or contrary to the definition of that term provided herein, the definition of that term provided herein applies and the definition of that term in the reference does not apply.